Brake installation for electrically driven vehicles

ABSTRACT

A brake installation for an electrically driven vehicle which includes mechanical brakes and utilizes the electric driving motor as electric brake by connecting it as generator, whereby the battery is recharged by this recovered energy; a control installation is provided which determines by way of a common brake lever, such as a brake pedal, the proportions in the overall brake deceleration shared by the mechanical brakes and the electric brake.

United States Patent 1 1 1 1 3,731,168 Strifler 14 1 May 1, 1973 [54]BRAKE INSTALLATION FOR [56] References Cited ELECTRICALLY DRIVENVEHICLES UNITED STATES PATENTS [75] Inventor: Paul Smile" Tack 3,546,54812/1970 Wouk ..318/139 7 Germany 3,530,356 9 1970 Aronson AssigneezDaimler-Benl Aktiengesenschaft, vll'lt, J1. Ct 81 ..3 I t Stuttgart- Unerturkhelm Germany Primary Examiner--Bemard A. Gilheany [22] Filed: Feb.5, 1970 Assistant Examiner-W. E. Duncanson, Jr. [21'] pp NO: 8,970Attorney-Craig, Antonelli, Stewart & HIill [57] ABSTRACT [30] ForeignApphcamm Pnomy Data A brake installation for an electrically drivenvehicle Feb.5,l969 Germany ..P 1905 641.8 which includes mechanicalbrakes and utilizes the l electric driving motor as electric brake byconnecting 52 US. Cl ..318/139, 318/371 i generator, whereby the batteryis recharged y 51 Int.Cl. ..H02p 3/16 this recovered gy; controlinstallation is P [581' Field 6: Search ..318/370, 371, 376, vided whichdetermines y y of a common brake lever, such as a brake pedal, theproportions in the over-all brake deceleration shared by the mechanicalbrakes and the electric brake.

14 Claims, 2 Drawing Figures PATENTEB MY 1 I975 INVENTOR PAUL E STRIFLERBRAKE INSTALLATION FOR ELECTRICALLY DRIVEN VEHICLES The presentinvention relates to a brake installation for electrically drivenvehicles which include a mechanical brake and an electric motor fed by abattery and adapted to be connected, for purposes of braking, asgenerator which supplies the energy thus recovered back to the battery.

Electrically driven vehicles can be electrically braked without wear inthat the electric motor is driven by the vehicle during the braking andacts as generator. As a result thereof, on the one hand, the electricbattery serving as energy source is recharged which leads to anenlargement of the radius of action whereas, on the other, themechanical brakes prone to wear are saved so that the length of lifethereof can be increased. Additionally, cold mechanical brakes areavailable for maximum braking effect in case of danger. However, limitsare imposed on the recovery of energy by means of charging the batteryby the respective charge condition of the battery. By reason of thegasing danger of the electrolyte of the battery, a predetermined voltagecannot be exceeded.

The present invention is concerned with the task to achieve with avehicle of the aforementioned type, the largest possible proportion ofthe brake deceleration, necessary from a traffic point of view,electrically and to utilize the same for the purpose of recovery ofenergy. The present invention essentially consists in that a controlinstallation is provided which in dependence on the charging conditionof the battery determines the proportion of the mechanical brake and ofthe electric brake adapted to be engaged by a common brake lever in theover-all brake deceleration. The advantage results from this arrangementthat the mechanical brake is far-reachingly saved and only the portionwhich under certain circumstances can no longer be braked electricallyby reason of the charge condition of the battery, is left over to themechanical brake.

In order to achieve that the driver does not notice anything of thischange of the brake deceleration distribution and achieves apredetermined brake deceleration with each brake actuating force, it isappropriate if the control installation determines the proportionalshares of the brakes in the overall deceleration in such a manner thatindependently of the distribution, a predetermined brake deceleration iscoordinated to each position of the brake lever. It is achieved therebythat always the same overall brake deceleration is coordinated to eachactuating force of the brake lever, for example, to the pedal force ofabrake pedal.

A structurally appropriate type of construction of the present inventionis obtained if the control installation adjusts a conventional brakevalve of the mechanical brake and a control resistance arranged in theenergizing circuit for the windings of the electric motor. Anelectromagnetic adjusting member may be provided thereby advantageouslyas control installation whose core or armature is connected with thebrake valve and with the resistance and whose coil is connected to acontrol device producing a current in dependence on the charge conditionand the temperature of the battery. Depending on the charging condition,the initial condition prior to the beginning or during a brakingoperation is determined by the core of the electromagnetic adjustingmember depending on the charging condition, i.e., it is determined howstrongly the com? mon brake lever of the mechanical and of the electricbrake acts on the associated brake valve and on the associated controlresistance.

It is advantageous if, for the purpose of controlling the electricbrake, the magnitude of the energization is adjustable by way of thebrake lever at the control resistance of the energizing circuit. Inorder to achieve that during actuation of the brake lever, at first theelectric brake starts to operate and only when the maximum possiblebrake deceleration for the electric brake dependent on the chargingcondition of the battery is exceeded, the mechanical brake isadditionally engaged, the brake lever may be connected with the brakevalve by way of a link, for example, a conventional lost-motion link,and may actuate the brake valve only after traversing a predeterminedpath which corresponds to the maximum electric brake decelerationdependent on the charging condition of the battery. In order to have thefull brake deceleration immediately available nonetheless in case ofdanger, a damping element may be built into the link which bridges orby-passes the link during rapid actuation of the brake lever. Thisdamping element which does not become operative during the normal brakeoperation,

brings about that during a sudden actuation of the brake lever, thecomplete brake deceleration of the mechanical brake is availableimmediately.

Accordingly, it is an object of the present invention to provide a brakeinstallation for electrically driven vehicles which avoids by simplemeans the aforementioned shortcomings and drawbacks encountered in theprior art.

Another object of the present invention resides in a brake installationfor electrically driven vehicles which maximizes the use of the electricmotor as electric brake for purposes of re-charging the electric batterywithout endangering the battery by excessive charging voltages.

A further object of the presentinvention resides in a brake installationfor electrically driven' vehicles in which a predetermined brakedeceleration is coordinated to each brake actuating force regardless ofthe distribution of the proportion of the brake deceleration shared bythe electric and mechanical brakes.

Still a further object of the present invention resides in'a brakeinstallation for electrically driven cars of the type described abovewhich is extremely reliable in operation, assures maximum safety, andmakes available the entire mechanical brake deceleration in case ofemergency. 1

These and further objects, features, and advantages of the presentinvention will become more obvious from the following description whichshows for purposes of illustration only, one embodiment in accordancewith the present invention, and wherein:

FIG. 1 is a schematic view of a brake installation according to thepresent invention of an electrically driven vehicle; and I FIG. 2 is adiagram representing the overall (entire) brake deceleration independence on the actuating force.

Referring now to the drawing and more particularly to FIG. 1, anelectric and a mechanical brake are simultaneously actuated by a commonbrake lever, in the illustrated embodiment by a brake pedal 1. Adoublelever 2 is connected with the brake pedal 1 which is pivotallyconnected by way of a spring link 3 with a lever 4 of the electricbrake. Upon actuation of the brake pedal 1, the lever 4 of the electricbrake sweeps over a control resistance 7 arranged in the energizingcircuit for the windings 5 of the electric motor 6 of the vehicle sothat with increasing pedal path and therewith with increasing pedalforce an increasing current is supplied by way of the energizing control8 to the windings 5 of the electric motor 6. Since this electric motor 6during braking acts as generator, the brake effect is increased on theone hand, with a continuing pedal path, whereas, on the other, theproduced energy returned to the battery 9 of the electric motor alsoincreases.

The second arm of the double lever 2 connected with the brake pedal 1acts on a conventional brake valve generally designated by referencenumeral 10. The connection of this lever arm 2 with the brake valve 10takes place by way of a link 11 which is so dimensioned that anactuation of the brake valve 10 takes place only when, as a result of afurther depressing of the brake pedal 1, a higher brake deceleration isdesired than can be supplied by the electric brake. When the end of theguide link 11, in the form of a lost-motion connection with an elongatedaperture cooperating with a pin is reached, at first the piston 13 of arelief valve 14 is closed by way of a spring 12 of the brake valve 10,and only thereafter the control valve 15 is forced off its seat in orderthat the air can from the reservoir tank (not shown) reach by way of theinlet 16 and by way of the outlet 17 the wheel brake cylinders (notshown). This pressure acts in a conventional manner also on the backside of the piston 13 so that a brake pressure corresponding to thepedal pressure or to the stress of the spring 12 is being built up inthe wheel cylinders. A

return spring 18 retains the link 11 in its end position.

In order to have the maximum possible brake deceleration instantaneouslyavailable in case of danger, a damping element 19 .is built into thelink 11 which during a rapid depressing of the brake pedal 1 bridges orby-passes the linkage 11 and actuates instantaneously the brake valve10. During the normal velocities, however, this damping element 19 iswithout influence for the actuation of the brake pedal 1.

In order to prevent that the battery 9 in the course of a brakingoperation is charged above the gasing voltage with the largest possibleelectric brake deceleration or heats up too strongly, a controlinstallation is provided which then changes-the distribution of theproportions of the mechanical brake and of the electric brake in theoverall brake deceleration, however, without changing the value of theoverall brake deceleration. For that purpose, an electromagneticadjusting member 20 is provided, to the core 21 of which is connected,on the one hand, the piston 13 of the brake valve 10 by way of a spring30, and, on the other, the electric control resistance 7 of theenergizing circuit of the windings 5 of the electric motor 6. The coil22 of the electromagnetic adjusting member 20 is connected with aconventional control device 23 which operates in dependence on thecharging voltage and on the temperature of the battery 9 andproducescurrent for the electromagnetic adjusting member 20. This, however,takes place only when the mechanical brake is actuated, i.e., when thecontact 24 arranged within the area of the double-lever 2 is closed.

The electromagnetic adjusting member 20 then displaces toward the rightas viewed in the drawing on the one hand, the control resistance 7,whereby the energizing current for the electric motor 6 is decreased. Asa result thereof, the electric deceleration is reduced to such an extentthat an acceptable value for the charging condition of the battery isachieved. However, since the overall brake deceleration is not to bechanged, the piston 13 of the brake valve 10 is simultaneously displacedalso toward the right as viewed in the drawing so that an assist of theforce of the spring 12 results. As a result of the displacement of thepiston 13, the pressure at the wheel brake cylindersis increased by wayof the control valve 15 until the backpressure at the back-side of thepiston 13 is in equilibrium with the increased pressure which iscomposed of the pressure of the spring 12 and of the force of theelectromagnetic adjusting member 20. The effect is thereby the same asif the driver would actuate more strongly the mechanical brakes.

In FIG. 2, the overall brake deceleration b is plotted in a diagramagainst brake pedal force P. The brake installation will be sodimensioned, especially by a matching of the springs 12 and 18, that abrake characteristic corresponding to the full line is achieved as brakedeceleration 25. This full line is composed, on the one hand, of thebrake deceleration 26 shown in dash line of the electric brake and, onthe other, of the brake deceleration 27 shown in dash and dot line ofthe mechanical brake. In the normal case, i.e., as long as the controlinstallation dependent on the battery 9 does not respond, the overallbrake deceleration 25 results as a composition of the lines 26 and 27.At first, only the electric brake is thereby engaged which can increaseup to a maximum deceleration by a change of the control resistance. Thismaximum value is determined by the output of the electric motor 6operating as generator. Only thereafter the mechanical brake isadditionally engaged, in case a higher brake deceleration becomesnecessary during the drive. This trailing of the mechanical brake isachieved by the linkage 11 in the actuating mechanism of the brake valve10. The link 11 is thereby so selected that the overall brakedeceleration 25 illustrated in full line is achieved.

If the charging condition of the battery 9 no longer permits that thebattery 9 is charged with the full output of the electric motor 6 actingas generator, then the control device 23 engages by way of theelectromagnetic adjusting member 20 in such a manner that by thedisplacement of the control resistance 7, the maximum electricdeceleration is limited to a lower value, for example, to the value 28illustrated in short dash lines. Simultaneously therewith, however, themechanical brake is engaged earlier by way of the electromagneticadjusting member 20, i.e., the beginning of the mechanical braking isdisplaced to the line 29 illustrated in dash and dot lines because thebrake valve 10 is actuated already by the electromagnetic adjustingmember 20. The matching is thereby made in such a manner that again theoverall brake deceleration 25 illustrated in full line is achieved sothat always an identical overall brake deceleration 25 is coordinated toeach pedal path or each pedal force independently of how the proportionsof the overall deceleration 25 are distributed to the mechanical brakeand to the electric brake.

While I have shown and described only one embodiment in accordance withthe present invention, it is understood that the same is not limitedthereto but is susceptible of numerous changes and modifications asknown to a person skilled in the art, and I therefore do not wish to belimited to the details shown and described herein but intend to coverall such changes and modifications as are encompassed by the scope ofthe appended claims.

I claim:

1. A brake installation for electrically driven vehicles which includesa mechanical brake and an electric motor operable to be connected as agenerator for braking purposes as an electric brake and fed bya battery,and in which the electric motor operating as a generator re-supplies theenergy recovered during braking to the battery, characterized in that adetecting means is provided for detecting the charging condition of thebattery and providing a signal indicative thereof, and a control meansis provided which is responsive to the detecting means and whichdetermines in dependence on the charging condition of the battery theproportional shares of the mechanical brake and of the electric brake inthe overall brake deceleration.

2. A brake installation according to claim 1, characterized in that saidcontrol meansincludes a common brake lever.

3. A brake installation according to claim 1, characterized in that themechanical brake includes brake valve means, in that a controlresistance means is operatively connected with the energizing circuitfor the windings of the electric motor, and in that the control means isoperable to adjust the brake valve means and the control resistancemeans.

4. A brake installation according to claim 3, characterized in that anelectromagneticadjusting member is provided in the control means whosecore is operatively connected with the brake valve means by way of aspring and with the control resistance means, and whose control windingis operatively connected with the detecting means which produces acurrent in dependence on the charging condition and on the temperatureof the battery.

5. A-brake installation according to claim 3, characterized in that themagnitude of the energization of the windings of the electric motor isadjustable by way of the brake lever at the control resistance means ofthe energizing circuit.

6. A brake installation according to claim 3, characterized in that thebrake lever is operatively connected with the brake valve means by wayof a link means and actuates the brake valve means only after traversinga predetermined path which corresponds to the maximum electric brakedeceleration dependent on the charging condition of the battery.

7. A brake installation according to claim 6, wherein said link meansincludes damping means which bypasses the link means during rapidactuation of the brake lever.

8. A brake installation for electrically driven vehicles which includesa mechanical brake and an electric motor operable to be connected as agenerator for braking purposes as an electric brake and fed by abattery, and in which the electric motor operating as a generatorre-supplies the energy recovered during braking to the battery,characterized in that a control means is provided which determines independence on the charging condition of the battery the proportionalshares of the mechanical brake and of the electric brake in the overallbrake deceleration, said control means including a common brake lever,the control means determining the proportional shares of the brakes inthe overall brake deceleration in such a manner that independently ofthe distribution, a predetermined brake deceleration is coordinated toeach position of the brake lever.

9. A brake installation according to claim 8, characterized in that themechanical brake includes brake valve means, in that a controlresistance means is operatively connected with the energizing circuitfor the windings of the electric motor, and in that the control means isoperable to adjust the brake valve means and the control resistancemeans.

10. A brake installation according to claim 9, characterized in that anelectromagnetic adjusting member is provided in the control means whosecore is operatively connected with the brake valve means by way of aspring and with the control resistance means, and whose control windingis operatively connected with a control device producing a current independence on the charging condition and on the temperature of thebattery.

11. A brake installation according to claim 10, characterized in thatthe magnitude of the energization of the windings of the electric motoris adjustable by way of the brake lever at the control resistance meansof the energizing circuit.

12. A brake installation according to claim 11, characterized in thatthe brake lever is operatively connected with the brake valve means byway of a link means and actuates the brake valve means only aftertraversing a predetermined path which corresponds to the maximumelectric brake deceleration dependent on the charging condition of thebattery.

13; A brake installation according to claim 12, wherein said link meansincludes damping means which by-passes the link means during rapidactuation of the brake lever.

14. A brake installation for electrically driven vehicles which includesa mechanical brake and an electric motor operable to be connected as agenerator for braking purposes as an electric brake and fed by abattery, and in which the electric motor operating as a generatorre-supplies the energy recovered during braking to the battery,characterized in that a control means is provided which determines independence on the charging condition of the battery the proportionalshares of the mechanical brake and of the electric brake in the overallbrake deceleration, the control means determining the proportionalshares of the brakes in the overall brake deceleration in such a mannerthat independently of the distribution, a predetermined brakedeceleration is coordinated to each position of the brake lever.

1. A brake installation for electrically driven vehicles which includesa mechanical brake and an electric motor operable to be connected as agenerator for braking purposes as an electric brake and fed by abattery, and in which the electric motor operating as a generatorre-supplies the energy recovered during braking to the battery,characterized in that a detecting means is provided for detecting thecharging condition of the battery and providing a signal indicativethereof, and a control means is provided which is responsive to thedetecting means and which determines in dependence on the chargingcondition of the battery the proportional shares of the mechanical brakeand of the electric brake in the overall brake deceleration.
 2. A brakeinstallation according to claim 1, characterized in that said controlmeans includes a common brake lever.
 3. A brake installation accordingto claim 1, characterized in that the mechanical brake includes brakevalve means, in that a control resistance means is operatively connectedwith the energizing circuit for the windings of the electric motor, andin that the control means is operable to adjust the brake valve meansand the control resistance means.
 4. A brake installation according toclaim 3, characterized in that an electromagnetic adjusting member isprovided in the control means whose core is operatively connected withthe brake valve means by way of a spring and with the control resistancemeans, and whose control winding is operatively connected with thedetecting means which produces a current in dependence on the chargingcondition and on the temperature of the battery.
 5. A brake installationaccording to claim 3, characterized in that the magnitude of theenergization of the windings of the electric motor is adjustable by wayof the brake lever at the control resistance means of the energizingcircuit.
 6. A brake installation according to claim 3, characterized inthat the brake lever is operatively connected with the brake valve meansby way of a link means and actuates the brake valve means only aftertraversing a predetermined path which corresponds to the maximumelectric brake deceleration dependent on the charging condition of thebattery.
 7. A brake installation according to claim 6, wherein said linkmeans includes damping means which by-passes the link means during rapidactuation of the brake lever.
 8. A brake installation for electricallydriven vehicles which includes a mechanical brake and an electric motoroperable to be connected as a generator for braking purposes as anelectric brake and fed by a battery, and in which the electric motoroperating as a generator re-supplies the energy recovered during brakingto the battery, characterized in that a control means is provided whichdetermines in dependence on the charging condition of the battery theproportional shares of the mechanical brake and of the electric brake inthe overall brake deceleration, said control means including a commonbrake lever, the control means determining the proportional shares ofthe brakes in the overall brake deceleration in such a manner thatindependently of the distribution, a predetermined brake deceleration iscoordinated to each position of the brake lever.
 9. A brake installationaccording to claim 8, characterized in that the mechanical brakeincludes brake valve means, in that a control resistance means isoperatively connected with the energizing circuit for the windings ofthe electric motor, and in that the control means is operable to adjustthe brake valve means and the control resistance means.
 10. A brakeinstallation according to claim 9, characterized in that anelectromagnetic adjusting member is provided in the control means whosecore is operatively connected with the brake valve means by way of aspring and with the control resistance means, and whose control windingis operatively connected with a control device producing a current independence on the charging condition and on the temperature of thebattery.
 11. A brake installation according to claim 10, characterizedin that the magnitude of the energization of the windings of theelectric motor is adjustable by way of the brake lever at the controlresistance means of the energizing circuit.
 12. A brake installationaccording to claim 11, characterized in that the brake lever isoperatively connected with the brake valve means by way of a link meansand actuates the brake valve means only after traversing a predeterminedpath which corresponds to the maximum electric brake decelerationdependent on the charging condition of the battery.
 13. A brakeinstallation according to claim 12, wherein said link means includesdamping means which by-passes the link means during rapid actuation ofthe braKe lever.
 14. A brake installation for electrically drivenvehicles which includes a mechanical brake and an electric motoroperable to be connected as a generator for braking purposes as anelectric brake and fed by a battery, and in which the electric motoroperating as a generator re-supplies the energy recovered during brakingto the battery, characterized in that a control means is provided whichdetermines in dependence on the charging condition of the battery theproportional shares of the mechanical brake and of the electric brake inthe overall brake deceleration, the control means determining theproportional shares of the brakes in the overall brake deceleration insuch a manner that independently of the distribution, a predeterminedbrake deceleration is coordinated to each position of the brake lever.